Closed
Description
rustc does not terminate (or will perhaps terminate with a stack overflow given sufficient time and insufficient memory) when provided the following code as input:
use std::marker::PhantomFn;
trait TypeTrans<X> : PhantomFn<(Self,X)> { type Y; }
trait Circular : PhantomFn<Self> {
type T : Circular;
}
impl<X, U : Circular> TypeTrans<X> for U {
type Y = < <U as Circular>::T as TypeTrans<X> >::Y;
}
fn main() {}
I expected an error message stating that the expansion recursion depth limit was exceeded (like when one makes such a mistake with C++ templates).
Instead, rustc does not terminate, and attaching gdb reveals an ever growing call stack (see backtrace below).
Meta
rustc --version --verbose:
rustc 1.0.0-dev (2b01a37ec 2015-02-21) (built 2015-02-21)
binary: rustc
commit-hash: 2b01a37ec38db9301239f0c0abcf3c695055b0ff
commit-date: 2015-02-21
build-date: 2015-02-21
host: x86_64-unknown-linux-gnu
release: 1.0.0-dev
Backtrace:
#0 0x00007ffff5431340 in middle::subst::EnumeratedItems$LT$$u27$a$C$$u20$T$GT$.Iterator::next::h1346200232120614734 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#1 0x00007ffff5430c18 in middle::ty_fold::TypeFolder::fold_substs::h2872510736836719091 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#2 0x00007ffff5431468 in middle::ty_fold::super_fold_trait_ref::h8139351459621092501 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#3 0x00007ffff5430655 in middle::ty_fold::TypeFolder::fold_ty::h6033027339639275593 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#4 0x00007ffff5430c5a in middle::ty_fold::TypeFolder::fold_substs::h2872510736836719091 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#5 0x00007ffff5431468 in middle::ty_fold::super_fold_trait_ref::h8139351459621092501 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#6 0x00007ffff5430655 in middle::ty_fold::TypeFolder::fold_ty::h6033027339639275593 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#7 0x00007ffff5430c5a in middle::ty_fold::TypeFolder::fold_substs::h2872510736836719091 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#8 0x00007ffff5431468 in middle::ty_fold::super_fold_trait_ref::h8139351459621092501 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#9 0x00007ffff5430655 in middle::ty_fold::TypeFolder::fold_ty::h6033027339639275593 () from /scratch/opt/lib/librustc-4e7c5e5c.so
#10 0x00007ffff5430c5a in middle::ty_fold::TypeFolder::fold_substs::h2872510736836719091 () from /scratch/opt/lib/librustc-4e7c5e5c.so
....